[linux-lvm] Segmentation fault in LVM2 latest version.

xiaowei xiaowei.hu at oracle.com
Fri Apr 11 01:14:40 UTC 2014

Hi Alasdair,

May I ask if you have a patch to test for this now?

On 03/18/2014 12:04 PM, Alasdair G Kergon wrote:
> On Fri, Mar 14, 2014 at 09:05:09AM +0800, xiaowei wrote:
>> That's great you reproduced this bug:)
>> So the fix could be easy?
> No.  Once you know what's wrong, you can find several more classes
> of lvextend that misbehave.
> I do have a prototype fix that deals with the case you hit, but it's not
> complete yet.
> There are two ways you can extend an LV:
>    1. By pairing up newly-allocated areas of disk with existing ones
>       as you go along.
>       (A simple example would be extending each existing stripe on the same
>       disk.)
>    2. By finding possible areas of disk to fit the required
>       number of areas then selecting the most appropriate ones.
>       (The general case.)
> You can also have a combination of the two, with some areas from 1
> and some from 2.
> The first is 'PREFERRED' in the code, and the second is 'USE_AREA'.
> The path through the code that you hit tried to use the first
> method when it should have used the second.
> (If the number of stripes is changing there's no trivial way to
> 'pair up' the new areas with the existing ones.)
> Minor structural changes are needed (code clean up) so that the
> cling policy can sometimes use the second method.
> The default 'allocation/maximise_cling' option fails.
> Alasdair

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